During take off and landing, the hot gas efflux, which we will refer to hereinafter as the jet or jets, from the lifting engines or fans of a VSTOL aircraft strike the ground and produce complex fluid flows around the aircraft, often resulting in substantial and unfavourable aerodynamic and environmental effects on aircraft operations.
The effects caused by the interaction between the ground and the VSTOL aircraft's jets include:
1. Ground jet sheets PA0 2. Fountain flows due to ground jet interaction where there are jets from two or more exhaust sources on the aircraft PA0 3. Hot gas ingestion of the engine or fan exhaust by the air intakes PA0 4. Downwash induced mainly by ground jet entrainment, on the aircraft's surfaces ("suck-down") PA0 5. Ground or deck erosion and/or heating PA0 6. Debris and dust ingestion into air intakes PA0 7. Thermal and acoustic fatigue on the aircraft structure and equipment
Re-circulation of hot exhaust gases into the engine intakes can result in large thrust losses, or even compressor stall. Variations of aircraft lift due to downwash induced by ground jet entrainment also degrade VSTOL performance. The hot upwash flows and the sound pressure generated by the exhaust jets and their interaction with the ground may result in thermal and acoustic fatigue of the aircraft structure and equipment. Ground erosion due to the high temperature, high pressure jets, ingestion of debris thrown up by the ground impinging jets and the reduction in pilot visibility due to dust cloud creation are other major problems. These latter problems are exacerbated when the VSTOL aircraft is operating from non-permanent surfaces such as desert or natural terrain, whilst some of the problems above arise in ship-borne or more conventional operating environments.
To counter these problems it is known to use prefabricated aluminium sheeting to protect the ground surface during VSTOL aircraft operations on land. For ship-borne operations, an anti-skid surface known as "Camrex" is painted onto thick steel plate for protection of the ships decking against erosion and heat. These known protective measures are not designed to improve aircraft performance in terms of reduced hot gas ingestion, ground effect lift loss, and debris/dust ingestion.
The problems mentioned above will be further exacerbated by the introduction of VSTOL aircraft with high temperature, high pressure exhausts.